// Copyright (c) 2012- PPSSPP Project.

// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, version 2.0 or later versions.

// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License 2.0 for more details.

// A copy of the GPL 2.0 should have been included with the program.
// If not, see http://www.gnu.org/licenses/

// Official git repository and contact information can be found at
// https://github.com/hrydgard/ppsspp and http://www.ppsspp.org/.

#include <algorithm>

#include "Common/GPU/OpenGL/GLFeatures.h"
#include "Common/LogReporting.h"
#include "Core/ConfigValues.h"
#include "GPU/Common/GPUStateUtils.h"
#include "GPU/GLES/DrawEngineGLES.h"
#include "GPU/GLES/FramebufferManagerGLES.h"
#include "GPU/GLES/ShaderManagerGLES.h"
#include "GPU/GLES/TextureCacheGLES.h"

static const char *depth_dl_fs = R"(
#ifdef GL_ES
#ifdef GL_FRAGMENT_PRECISION_HIGH
precision highp float;
#else
precision mediump float;
#endif
#endif
#if __VERSION__ >= 130
#define varying in
#define texture2D texture
#define gl_FragColor fragColor0
out vec4 fragColor0;
#endif
varying vec2 v_texcoord;
uniform vec4 u_depthFactor;
uniform vec4 u_depthShift;
uniform vec4 u_depthTo8;
uniform sampler2D tex;
void main() {
  float depth = texture2D(tex, v_texcoord).r;
  // At this point, clamped maps [0, 1] to [0, 65535].
  float clamped = clamp((depth + u_depthFactor.x) * u_depthFactor.y, 0.0, 1.0);

  vec4 enc = u_depthShift * clamped;
  enc = floor(mod(enc, 256.0)) * u_depthTo8;
  // Let's ignore the bits outside 16 bit precision.
  gl_FragColor = enc.yzww;
}
)";

static const char *depth_vs = R"(
#ifdef GL_ES
precision highp float;
#endif
#if __VERSION__ >= 130
#define attribute in
#define varying out
#endif
attribute vec2 a_position;
varying vec2 v_texcoord;
void main() {
  v_texcoord = a_position * 2.0;
  gl_Position = vec4(v_texcoord * 2.0 - vec2(1.0, 1.0), 0.0, 1.0);
}
)";

struct DepthUB {
	float u_depthFactor[4];
	float u_depthShift[4];
	float u_depthTo8[4];
};

const UniformBufferDesc depthUBDesc{ sizeof(DepthUB), {
	{ "u_depthFactor", -1, -1, UniformType::FLOAT4, 0 },
	{ "u_depthShift", -1, -1, UniformType::FLOAT4, 16 },
	{ "u_depthTo8", -1, -1, UniformType::FLOAT4, 32 },
} };

static const char *stencil_dl_fs = R"(
#ifdef GL_ES
#ifdef GL_FRAGMENT_PRECISION_HIGH
precision highp float;
#else
precision mediump float;
#endif
#endif
#if __VERSION__ >= 130
#define varying in
#define texture2D texture
#define gl_FragColor fragColor0
out vec4 fragColor0;
#endif
varying vec2 v_texcoord;
lowp uniform usampler2D tex;
void main() {
  uint stencil = texture2D(tex, v_texcoord).r;
  float scaled = float(stencil) / 255.0;
  gl_FragColor = vec4(scaled, scaled, scaled, scaled);
}
)";

static const char *stencil_vs = R"(
#ifdef GL_ES
precision highp float;
#endif
#if __VERSION__ >= 130
#define attribute in
#define varying out
#endif
attribute vec2 a_position;
varying vec2 v_texcoord;
void main() {
  v_texcoord = a_position * 2.0;
  gl_Position = vec4(v_texcoord * 2.0 - vec2(1.0, 1.0), 0.0, 1.0);
}
)";

static bool SupportsDepthTexturing() {
	if (gl_extensions.IsGLES) {
		return gl_extensions.OES_packed_depth_stencil && (gl_extensions.OES_depth_texture || gl_extensions.GLES3);
	}
	return gl_extensions.ARB_texture_float;
}

static Draw::Pipeline *CreateReadbackPipeline(Draw::DrawContext *draw, const char *tag, const UniformBufferDesc *ubDesc, const char *fs, const char *fsTag, const char *vs, const char *vsTag) {
	using namespace Draw;

	const ShaderLanguageDesc &shaderLanguageDesc = draw->GetShaderLanguageDesc();

	ShaderModule *readbackFs = draw->CreateShaderModule(ShaderStage::Fragment, shaderLanguageDesc.shaderLanguage, (const uint8_t *)fs, strlen(fs), fsTag);
	ShaderModule *readbackVs = draw->CreateShaderModule(ShaderStage::Vertex, shaderLanguageDesc.shaderLanguage, (const uint8_t *)vs, strlen(vs), vsTag);
	_assert_(readbackFs && readbackVs);

	InputLayoutDesc desc = {
		{
			{ 8, false },
		},
		{
			{ 0, SEM_POSITION, DataFormat::R32G32_FLOAT, 0 },
		},
	};
	InputLayout *inputLayout = draw->CreateInputLayout(desc);

	BlendState *blendOff = draw->CreateBlendState({ false, 0xF });
	DepthStencilState *stencilIgnore = draw->CreateDepthStencilState({});
	RasterState *rasterNoCull = draw->CreateRasterState({});

	PipelineDesc readbackDesc{
		Primitive::TRIANGLE_LIST,
		{ readbackVs, readbackFs },
		inputLayout, stencilIgnore, blendOff, rasterNoCull, ubDesc,
	};
	Draw::Pipeline *pipeline = draw->CreateGraphicsPipeline(readbackDesc, tag);
	_assert_(pipeline);

	rasterNoCull->Release();
	blendOff->Release();
	stencilIgnore->Release();
	inputLayout->Release();

	readbackFs->Release();
	readbackVs->Release();

	return pipeline;
}

bool FramebufferManagerGLES::ReadbackDepthbufferSync(Draw::Framebuffer *fbo, int x, int y, int w, int h, uint16_t *pixels, int pixelsStride) {
	using namespace Draw;

	if (!fbo) {
		ERROR_LOG_REPORT_ONCE(vfbfbozero, SCEGE, "ReadbackDepthbufferSync: bad fbo");
		return false;
	}
	// Old desktop GL can download depth, but not upload.
	if (gl_extensions.IsGLES && !SupportsDepthTexturing()) {
		return false;
	}

	// Pixel size always 4 here because we always request float or RGBA.
	const u32 bufSize = w * h * 4;
	if (!convBuf_ || convBufSize_ < bufSize) {
		delete[] convBuf_;
		convBuf_ = new u8[bufSize];
		convBufSize_ = bufSize;
	}

	const bool useColorPath = gl_extensions.IsGLES;
	bool format16Bit = false;

	if (useColorPath) {
		if (!depthReadbackPipeline_) {
			depthReadbackPipeline_ = CreateReadbackPipeline(draw_, "depth_dl", &depthUBDesc, depth_dl_fs, "depth_dl_fs", depth_vs, "depth_vs");
			depthReadbackSampler_ = draw_->CreateSamplerState({});
		}

		shaderManager_->DirtyLastShader();
		auto *blitFBO = GetTempFBO(TempFBO::COPY, fbo->Width(), fbo->Height());
		draw_->BindFramebufferAsRenderTarget(blitFBO, { RPAction::DONT_CARE, RPAction::DONT_CARE, RPAction::DONT_CARE }, "ReadbackDepthbufferSync");
		Draw::Viewport viewport = { 0.0f, 0.0f, (float)fbo->Width(), (float)fbo->Height(), 0.0f, 1.0f };
		draw_->SetViewports(1, &viewport);

		draw_->BindFramebufferAsTexture(fbo, TEX_SLOT_PSP_TEXTURE, FB_DEPTH_BIT, 0);
		draw_->BindSamplerStates(TEX_SLOT_PSP_TEXTURE, 1, &depthReadbackSampler_);

		// We must bind the program after starting the render pass.
		draw_->SetScissorRect(0, 0, w, h);
		draw_->BindPipeline(depthReadbackPipeline_);

		DepthUB ub{};

		if (!gstate_c.Use(GPU_USE_ACCURATE_DEPTH)) {
			// Don't scale anything, since we're not using factors outside accurate mode.
			ub.u_depthFactor[0] = 0.0f;
			ub.u_depthFactor[1] = 1.0f;
		} else {
			const float factor = DepthSliceFactor();
			ub.u_depthFactor[0] = -0.5f * (factor - 1.0f) * (1.0f / factor);
			ub.u_depthFactor[1] = factor;
		}
		static constexpr float shifts[] = { 16777215.0f, 16777215.0f / 256.0f, 16777215.0f / 65536.0f, 16777215.0f / 16777216.0f };
		memcpy(ub.u_depthShift, shifts, sizeof(shifts));
		static constexpr float to8[] = { 1.0f / 255.0f, 1.0f / 255.0f, 1.0f / 255.0f, 1.0f / 255.0f };
		memcpy(ub.u_depthTo8, to8, sizeof(to8));

		draw_->UpdateDynamicUniformBuffer(&ub, sizeof(ub));

		// Fullscreen triangle coordinates.
		static const float positions[6] = {
			0.0, 0.0,
			1.0, 0.0,
			0.0, 1.0,
		};
		draw_->DrawUP(positions, 3);

		draw_->CopyFramebufferToMemorySync(blitFBO, FB_COLOR_BIT, x, y, w, h, DataFormat::R8G8B8A8_UNORM, convBuf_, w, "ReadbackDepthbufferSync");

		textureCache_->ForgetLastTexture();
		// TODO: Use 4444 so we can copy lines directly (instead of 32 -> 16 on CPU)?
		format16Bit = true;
	} else {
		draw_->CopyFramebufferToMemorySync(fbo, FB_DEPTH_BIT, x, y, w, h, DataFormat::D32F, convBuf_, w, "ReadbackDepthbufferSync");
		format16Bit = false;
	}

	if (format16Bit) {
		// In this case, we used the shader to apply depth scale factors.
		uint16_t *dest = pixels;
		const u32_le *packed32 = (u32_le *)convBuf_;
		for (int yp = 0; yp < h; ++yp) {
			for (int xp = 0; xp < w; ++xp) {
				dest[xp] = packed32[xp] & 0xFFFF;
			}
			dest += pixelsStride;
			packed32 += w;
		}
	} else {
		// TODO: Apply this in the shader?  May have precision issues if it becomes important to match.
		// We downloaded float values directly in this case.
		uint16_t *dest = pixels;
		const GLfloat *packedf = (GLfloat *)convBuf_;
		DepthScaleFactors depthScale = GetDepthScaleFactors();
		for (int yp = 0; yp < h; ++yp) {
			for (int xp = 0; xp < w; ++xp) {
				float scaled = depthScale.Apply(packedf[xp]);
				if (scaled <= 0.0f) {
					dest[xp] = 0;
				} else if (scaled >= 65535.0f) {
					dest[xp] = 65535;
				} else {
					dest[xp] = (int)scaled;
				}
			}
			dest += pixelsStride;
			packedf += w;
		}
	}

	gstate_c.Dirty(DIRTY_ALL_RENDER_STATE);
	return true;
}

// Well, this is not depth, but it's depth/stencil related.
bool FramebufferManagerGLES::ReadbackStencilbufferSync(Draw::Framebuffer *fbo, int x, int y, int w, int h, uint8_t *pixels, int pixelsStride) {
	using namespace Draw;

	if (!fbo) {
		ERROR_LOG_REPORT_ONCE(vfbfbozero, SCEGE, "ReadbackStencilbufferSync: bad fbo");
		return false;
	}

	const bool useColorPath = gl_extensions.IsGLES;
	if (!useColorPath) {
		return draw_->CopyFramebufferToMemorySync(fbo, FB_STENCIL_BIT, x, y, w, h, DataFormat::S8, pixels, pixelsStride, "ReadbackStencilbufferSync");
	}

	// Unsupported below GLES 3.1 or without ARB_stencil_texturing.
	// OES_texture_stencil8 is related, but used to specify texture data.
	if ((gl_extensions.IsGLES && !gl_extensions.VersionGEThan(3, 1)) && !gl_extensions.ARB_stencil_texturing)
		return false;

	// Pixel size always 4 here because we always request RGBA back.
	const u32 bufSize = w * h * 4;
	if (!convBuf_ || convBufSize_ < bufSize) {
		delete[] convBuf_;
		convBuf_ = new u8[bufSize];
		convBufSize_ = bufSize;
	}

	if (!stencilReadbackPipeline_) {
		stencilReadbackPipeline_ = CreateReadbackPipeline(draw_, "stencil_dl", &depthUBDesc, stencil_dl_fs, "stencil_dl_fs", stencil_vs, "stencil_vs");
		stencilReadbackSampler_ = draw_->CreateSamplerState({});
	}

	shaderManager_->DirtyLastShader();
	auto *blitFBO = GetTempFBO(TempFBO::COPY, fbo->Width(), fbo->Height());
	draw_->BindFramebufferAsRenderTarget(blitFBO, { RPAction::DONT_CARE, RPAction::DONT_CARE, RPAction::DONT_CARE }, "ReadbackStencilbufferSync");
	Draw::Viewport viewport = { 0.0f, 0.0f, (float)fbo->Width(), (float)fbo->Height(), 0.0f, 1.0f };
	draw_->SetViewports(1, &viewport);

	draw_->BindFramebufferAsTexture(fbo, TEX_SLOT_PSP_TEXTURE, FB_STENCIL_BIT, 0);
	draw_->BindSamplerStates(TEX_SLOT_PSP_TEXTURE, 1, &stencilReadbackSampler_);

	// We must bind the program after starting the render pass.
	draw_->SetScissorRect(0, 0, w, h);
	draw_->BindPipeline(stencilReadbackPipeline_);

	// Fullscreen triangle coordinates.
	static const float positions[6] = {
		0.0, 0.0,
		1.0, 0.0,
		0.0, 1.0,
	};
	draw_->DrawUP(positions, 3);

	draw_->CopyFramebufferToMemorySync(blitFBO, FB_COLOR_BIT, x, y, w, h, DataFormat::R8G8B8A8_UNORM, convBuf_, w, "ReadbackStencilbufferSync");

	textureCache_->ForgetLastTexture();

	// TODO: Use 1/4 width to write all values directly and skip CPU conversion?
	uint8_t *dest = pixels;
	const u32_le *packed32 = (u32_le *)convBuf_;
	for (int yp = 0; yp < h; ++yp) {
		for (int xp = 0; xp < w; ++xp) {
			dest[xp] = packed32[xp] & 0xFF;
		}
		dest += pixelsStride;
		packed32 += w;
	}

	gstate_c.Dirty(DIRTY_ALL_RENDER_STATE);
	return true;
}